Electric distribution system



July 6, 1943. H. E. PEARSON 2,323,418

ELECTRIC DISTRIBUTION SYSTEM Filed June 11, 1941 INVENTOR Ak /P0105 f d-796804 Patented July 6, 1943 2,323,418 ELECTRIC DISTRIBUTION SYSTEM Harold E. Pearson, Bethlehem, Pa., assignor, by

mesne assignments, to The Pennsylvania Company for Insurances on Lives and Granting Annuities, Philadelphia, Pa., a corporation of Pennsylvania Application June 11, 1941, Serial No. 397,524

6 Claims.

This invention relate particularly to systems of distribution wherein a main circuit supplies feeder circuits which in turn supply translating devices connected thereto; and the feeder circuits may be connected to a net-work supplying the translating devices.

Circuit interrupting devices, such as automatic circuit breakers, are introduced in such systems between the feeders and the main supply circuit and it is desirable to make such circuit interrupting devices of an interrupting capacity sufficient to take care of expected overload currents; but where extreme or abnormally high currents arise, such as upon the occurrence of short-circuits, the feeder interrupting devices should be protected from the necessity of interrupting such high current values. With such protection, the feeder circuit interrupters may be made of much smaller interrupting capacity than would other- Wise be necessary. And it is highly desirable to make the feeder breakers of small interrupting capacity as small places only are usually available for their installation, such as manholes in the cities or towns supplied. Also the smaller the currents interrupted in such locations the less becomes the danger from fire hazard and the discharge of high temperature gases under high pressure.

The main object of this invention is to provide means for protecting the feeder circuit interrupting devices or breakers from the necessity of interrupting their circuits when the current values are extreme, such as upon the occurrence of pronounced short-circuits. Another object is to permit the feeder circuit breakers to be of lower current interrupting capacity and of smaller size than would otherwise be required. Another object is to provide auxiliary control means, such as by relays and their connections, which will be of a simple and dependable character. Other objects and advantages will be understood from the following description and accompanying drawing.

The drawing is a diagram showing a preferred embodiment of the invention.

Main supply circuits have previously been divided into sections and such division into sections, as in a sectional loop system, is utilized in the present invention. Such sections are connected together by main circuit breakers of high current interrupting capacity and may be located at sub-stations.

Referring to the drawing, the main supply line is indicated as divided into sections Ia, Ib and I and as continuing to other adjoining sections. A

two line circuit is shown for simplicity, although instead of a single phase circuit the suppl line may be of the usual three-phase type, or of any other form. Main circuit breakers 2a and 2b are shown connecting the adjoining sections and these may be of any suitable form, the same being indicated diagrammatically of a simple character for clearness. Trip relays 3a and 3b are indicated for automatically opening the main circuit breakers; and these relays are controlled by overload quick acting relays 4a and 41). These relays in their unattracted positions close a circuit through fixed contacts 5 and 5a and when sufficiently energized, these relays close a circuit between fixed contacts 6 and 6a. The relays 4a and 4b are responsive to overload in the main line circuit being respectively connected to current transformers la and lb related to the main line circuit. The coils of the trip relays 3a and 3b are energized to trip the main circuit breakers when the relays 4a and 4b are respectively actuated to their attracted positions. They then engage the contacts 6 and 6a which respectively energize the trip coils of the relays 3a and 31). These trip coils are then energized from an auxiliary circuit indicated as being supplied from a battery 8, the circuit through the trip coils being from the positive line 8a through the trip coils and contacts to and 6 to the negative line 8b.

Introduced in the main line circuit across the contacts of each of the main line circuit breakers is an impedance device or reactor 9 having comparatively high impedance. Thus when one of the main circuit breakers is opened, it will introduce in the main line circuit its respective reactors and thereby reduce the magnitude in the main line in the particular section affected for the purpose hereafter explained. Each section of the main line may supply a number of feeder circuits and in the drawing one feeder circuit I0 is indicated as being supplied from each section. Each feeder circuit is shown controlled by an automatic circuit breaker I I controlled by a tripping relay I2. This relay is in turn controlled by a time delay relay I3 which may be of any suitable form and is indicated as being retarded in its movement from its unattracted position to its attracted position by a dashpot I3a. The relay I3 is an overload relay having its winding controlled by a current transformer I4 related to the feeder circuit. When the relay I3 is sufficiently energized it will connect the contacts I5 and I5a. The contact IE1: is connected to one terminal of the trip coil of relay I2 and the contact I5 is connected to the negative line 8b. The

other terminal of the trip coil of relay I2 is connected to a line It which is adapted to be of positive potential under normal conditions but under abnormal conditions, such as upon the occurrence of a pronounced overload, it loses it potential which is restored only after the affected main line circuit breaker has been opened. Under normal conditions the circuit from the hue it passes by the Wire lfia through the contacts and 5a of the circuit breaker 2a and then through the contacts 5 and 5a of the circuit breaker 2b and then to the positive line 8a. This circuit would include in series the contacts 5 and 5a of each of the main line circuit breaker and it follows that in case any one or the overload relays of the main line circuit breakers was sufficiently energized to be moved to its attracted position, the line or pilot Wire l6 would lose its potential.

It is sometimes necesary for replacement or repairs that circuit breakers be temporarily removed and for this purpose it is common to provide drawout type breakers and in case such type breakers be used, provision should be made for maintaining th energization of the line It when any main line circuit breaker is drawn out. In the drawing there is generally indicated a series of main disconnect contacts ll and auxiliary disconnect contacts it. The disconnect contacts which are connected to the contacts 5 and 5a of each breaker are indicated as having yieldable spring contacts H! which, when the main circuit breaker is in place, will be separated by an insulating projection but when the circuit breaker is withdrawn, this insulating element will be withdrawn with the removal of the circuit breaker and the contacts 19 thereby permitted to engage each other so as to maintain positive potential on the line l3 when any circuit breaker is withdrawn.

In operation, upon the occurrence of any normal overloads, the affected feeder circuit breaker will be opened automatically by its overload relay closing the circuit between the contacts 15 and 150,, the pilot line it being then energized because no one of the main line circuit breakers will be open as their overload relays are set so as not to be affected by normal overload currents in the feeder circuits. The opening of any one of the feeder circuit breakers under moderate overload conditions will require a persistence of such overload a short time interval because their overload relays are time delay relays.

In case the overload in any one feeder circuit is extreme, such as caused by a pronounced shortcircuit, the main circuit breaker supplying the section to which the affected feeder is connected, will be immediately opened by its quick acting relay causing the circuit between the contacts 6 and do, to be closed. Such action opens the contacts 5 and 5a which removes th positive potential from the line it; and owing to the fact that the overload relays of the feeder circuit breakers are time delay relays, the main circuit breaker will open and remove the potential from the line [6 before the feeder overload relay has had time to act to close the contacts l5 and 51. The opening of the affected main circuit breaker will introduce the high impedance reactors 9 in the main line circuit and thereby reduce the current supplied to the affected feeder circuit. After the mainline circuit breaker ha opened, its overload relay will be deenergized because the portions of the main circuit supplying energy to the current transformers la, lb are shunted by the impedance devices 9. The deenergization of the an. no,

overload relay of the affected main circuit breaker will cause the contacts 5 and 5a to be reclosed which then restores positive potential to the line l6. This permits the overload relay of the affected feeder circuit breaker to energize its trip coil l2 by closing the circuit from the positive line I6 to the negative line 25b. The affected feeder circuit breaker will then be opened automatically and thereby disconnect the affected feeder circuit from the main line. At the time the feeder circuit is thus opened, th reactors 9 have been introduced in the main line circuit to the affected section and it follows that the feeder circuit breaker is then required to interrupt a current of much less value than would otherwise be the case because in the meantime.

the reactors 9 have been introduced in the main line circuit to the feeder and thereby reduced the current from a high value to one within the circuit interrupting capacity of the feeder breaker. The main line affected circuit breaker may then be reclosed at the sub-station. Such closing of the main breaker Will short-circuit the reactors S and remove them from the path of the main line current.

In some cases more than one of the main line circuit breakers may be operated upon the occurrence of a pronounced overload by reason of their quick acting overload current relays and in such an event will introduce into the main line circuit the reactors related to such circuit breakers and thereby further reduce the current to the affected feeder; and the circuit breaker of the affected feeder cannot be opened until after the opening of th main line circuit breakers.

By reason of the fact that the contacts 5 and 5a of each main line circuit breaker is included in series with the corresponding contacts of each main line circuit breaker, it follows that upon the drawout of any main line circuit breaker, the line I6 could not be maintained at its potential unless maintaining contacts were provided for this circuit upon the drawout of the circuit breaker in some manner, such as that already described with reference to the contacts l9.

Although one embodiment of this invention has been particularly described, it Will be understood that various modifications may be made for insuring the opening of a main line circuit breaker upon the occurrence of pronounced overload current and thereby reducing the current to the affected feeder circuit or circuits, before the affected feeder circuit breaker is permitted to open and yet permit the opening of the feeder circuit breakers under normal overload conditions without necessitating the prior opening of one or more main line circuit breaker or breakers.

I claim:

1. A system of distribution comprising a main supply circuit divided into sections, main automatic overload circuit breakers connecting said sections successively in series with each other, impedance devices in series in said main circuit connected between said sections and normally short-circuited by said circuit breakers respectively, feeder circuits connected respectively to said sections, and automatic overload circuit breakers in the feeder circuits respectively, said main breakers and feeder breakers having related control means for causing an affected main breaker to open before its related feeder breaker upon the occurrence of pronounced overload.

2. A system of distribution comprising a main supply circuit divided into sections, main automatic overload circuit breakers connecting said sections successively in series with each other, impedance devices in series in said main circuit connected between said sections and normally short-circuited by said circuit breakers respectively, feeder circuits connected respectively to said sections, and automatic overload circuit breakers in the feeder circuits respectively, said main breakers having quick acting overload relays and said feeder breakers having time delay overload relays.

3. A system of distribution comprising a main supply circuit divided into sections, main automatic overload circuit breakers connecting said sections successively in series with each other, impedance devices in series in said main circuit connected between said sections and normally short-circuited by said circuit breakers respectively, feeder circuits connected respectively to said sections, and automatic overload circuit breakers in the feeder circuits respectively, said main breakers having quick acting overload relays and said feeder breakers having time delay overload relays, and a control circuit connected between said main breakers and feeder breakers for preventing the opening of said feeder breakers until after the opening of the main breakers upon the occurrence of pronounced overload.

4. A system of distribution comprising a main supply circuit divided into sections, main automatic overload circuit breakers connecting said sections successively in series with each other, impedance devices in series in said main circuit connected between said sections and normally short-circuited by said circuit breakers respectively, feeder circuits connected respectively to said sections, and automatic overload circuit breakers in the feeder circuits respectively, said main breakers having quick acting overload relays and said feeder breakers having time delay overload relays, and a normally closed control circuit related to each of said main breakers and feeder breakers openable by the actuation of the overload relay of each of said breakers for pre venting the opening of a related feeder breaker until after the opening of the main breaker upon the occurrence of pronounced overload.

5. A system of distribution comprising a main supply circuit divided into sections, main automatic overload circuit breakers connecting said sections successively in series with each other, impedance devices in series in said main circuit connected between said sections and normally short-circuited by said circuit breakers respectively, feeder circuits connected respectively to said sections, and automatic overload circuit breakers in the feeder circuits respectively, said main breakers having quick acting overload relays and said feeder breakers having time delay overload relays, a normally closed control circuit related to each of said main breakers and feeder breakers openable by the actuation of the overload relay of each of said breakers for preventing the opening of a related feeder breaker until after the opening of the main breaker upon the occurrence of pronounced overload, and means for maintaining said control circuit closed at any main breaker upon the removal from position of such main breaker.

6. A system of distribution comprising a main supply circuit, a feeder circuit, a main circuit breaker in the main circuit having a quick acting overload relay supplied with energy derived from a portion of the main circuit for opening the main breaker on pronounced overloads, a feeder circuit breaker in the feeder circuit having a time delay overload relay for opening the feeder circuit upon the occurrence of overload therein, a control circuit for supplying current for controlling the opening of the feeder breaker, said control circuit having contacts closed by said quick acting overload relay when in its unattracted position and opened when in its attracted position, and an impedance device connected in shunt to the terminals of said main ,circuit breaker and to said portion of the main circuit for reducing the current to the feeder circuit upon the opening of said main circuit breaker and for insuring said quick acting overload relay being restored to its unattracted position for permitting the opening of said feeder circuit breaker after the opening of said main circuit breaker.

HAROLD E. PEARSON. 

